Quantum physics or quantum mechanics

 Quantum physics, or quantum mechanics, is a fundamental branch of physics that deals with the behavior of matter and energy at the smallest scales, such as atoms and subatomic particles. Unlike classical physics, which describes the macroscopic world, quantum physics explains phenomena that occur at the atomic and subatomic levels, where particles like electrons, photons, and others exhibit wave-particle duality and exist in probabilistic states rather than definitive ones.

Some key principles of quantum physics include:

1. Wave-particle duality: Particles, such as electrons and photons, can behave both as particles and waves depending on the experiment being conducted. This was first observed in the famous double-slit experiment.

2. Superposition: A particle can exist in multiple states or locations simultaneously. It's only when measured or observed that it "collapses" into a definite state.

3. Quantum entanglement: Particles that become entangled affect each other instantaneously, no matter how far apart they are. If one particle's state changes, the other entangled particle’s state will also change instantaneously.

4. Uncertainty Principle: Introduced by Werner Heisenberg, this principle states that it is impossible to know both the exact position and the exact momentum of a particle at the same time. The more precisely one is known, the less precisely the other can be measured.

5. Quantization of Energy : Energy in quantum systems is not continuous but comes in discrete amounts, called "quanta." For example, an electron in an atom can only exist in specific energy levels.

Quantum physics has revolutionized our understanding of the universe and has led to the development of technologies such as semiconductors, lasers, quantum computing, and more. It's a field filled with paradoxes and counterintuitive results, but it's extremely accurate in describing the behavior of the microscopic world.